Compressed gas, such as carbon dioxide (CO2), has been used to drive or “power” various devices. For instance, CO2 has been employed for powering pneumatic tools, such as tools that are used in automotive applications (e.g., off-road applications, such as air chucks for airing up tires, etc.), construction applications (e.g., for powering nail guns, staple guns, wrenches, saws, sanders, grinders, buffers, drills, hammers, chisels, painters, blow guns, grease guns, caulking guns, shears, ratchets, etc.), industrial applications, manufacturing applications (e.g., semiconductor fabrication applications, etc.), and various other applications. CO2 has also been employed as a propellant, such as for use in dispensing a liquid solution, such as beverages, sanitizing solutions, pesticide solutions, etc. In any such application, whether driving a pneumatic tool or serving as a propellant, CO2 is referred to herein as “driving” (or “powering”) the device, and thus any such device is referred to herein as being CO2 driven (or powered). For instance, when being used in a pneumatic tool application, the CO2 drives the operation of the pneumatic tool; whereas when being used as a propellant, the CO2 drives the output of the target solution (e.g., through a spray nozzle or other output interface).
Gases other than CO2, such as nitrogen, are employed in some compressed gas-driven devices. However, CO2 is a particularly popular gas to use for many compressed gas-driven devices because of the often-desired quality that it maintains constant amount of pressure or power until the CO2 storage cylinder completely empties. That is, contrary to nitrogen and many other inert gases, the output pressure generated by CO2 does not change as the amount of CO2 remaining in the storage cylinder reduces, until the cylinder empties of CO2. Thus, largely why CO2 is popular for driving pneumatic tools and as a propellant is because it provides a steady pressure rate. Other inert gases may be used as the gas source for compressed gas-driven devices, but inconsistency in pressure may have to be addressed when using those other gases (e.g., as the gas reduces out of the gas storage cylinder, pressure loss may occur).
CO2 is often employed as an externally-supplied propellant source for dispensing some tar-et solution. For instance, a CO2 storage cylinder may be used for outputting a flow of CO2 as a propellant for dispensing a separately-stored target solution (e.g., liquid solution) that is stored external to the CO2 storage cylinder. For instance, the target solution to be dispensed may be a beverage, sanitizing solution, pesticide, etc. As the CO2 flow is output, the separately-stored target solution (e.g., liquid solution) may be mixed with and/or carried/propelled by the CO2. In contrast, in some instances, CO2 or other gas propellant may be implemented as a propellant within an aerosol application. An aerosol is, by definition, a gaseous suspension of a fine solid or liquid particle. Thus, in an aerosol application, a substance such as paint, detergent, pesticide, etc. is packaged under pressure with the gaseous propellant (e.g., CO2) for release as a spray of fine particles. Accordingly, in the aerosol application, the target solution (e.g., liquid solution) to be dispensed is premixed with and packaged together with the gas propellant in a common storage cylinder. However, in general, CO2 has not gained great popularity for use in aerosol applications due, in part, to corrosive effects that the CO2 has when combined with certain liquids, especially water, on many aerosol containers, thereby reducing shelf-life of the aerosol containers. In view of the above, in a propellant application, CO2 (or other gas) may be used as an aerosol propellant in which it is mixed and stored with the target solution to be dispensed, or it may be implemented as a separate/external propellant source that is stored separate from the target solution to be dispensed.
In general, there are two types of liquefied CO2 cylinders in commercial use: 1) the so-called standard type (sometimes called “gas” or “vapor” type), and 2) the so-called siphon type. Both the standard and siphon types of CO2 cylinders contain liquefied CO2 in them as long as they are filled. A standard cylinder stands upright and releases gas from the evaporation of the CO2 liquid when the valve is opened. Thus, the standard cylinder discharges gas in an upright position, and it discharges liquid when inverted. Siphon cylinders have a dip tube from the valve to the bottom of the cylinder so that when the valve is opened liquid CO2 comes out without having to invert the bottle. Thus, the siphon cylinder discharges liquid when the cylinder is in the upright position. The discharged liquid may be dispensed in certain applications, or it may be converted to gas through heating after it is dispensed from the cylinder. For instance in certain applications, the discharged CO2 liquid is heated to convert it to gas, and the resulting gas is used to drive an end device (e.g., as a propellant or as an air power supply for a pneumatic device). Standard and siphon types of CO2 cylinders are well known in the art, see e.g., “Handbook of Compressed Gases”, by Compressed Gas Association, Edition: 4, illustrated, revised. Published by Springer, 1999, ISBN 0412782308, 9780412782305, (particularly see pages 295-311).
The operation of CO2 for driving a device (e.g., either for driving a pneumatic device or for serving as a propellant) is well known in the art, and is thus only briefly discussed herein. The following discussion concerning the operation of CO2 for driving a device is intended only for general informative purposes to aid the reader in understanding that operation of the CO2 for driving a device generally results in reduced temperature/cooling, and the discussion is not intended to be limiting of the scope of the concepts presented herein in any way. During typical operation of CO2-driven devices, the liquid CO2 stored in the CO2 storage cylinder converts from liquid to gas. The conversion from liquid to gas causes a reduction in temperature, which causes the cylinder to get cold. During typical operation, there usually exists both liquid and gas in the CO2 storage cylinder. As CO2 gas and/or liquid is output from the cylinder to drive a device (e.g., either to drive a pneumatic device or to act as a propellant), remaining liquid in the cylinder evaporates to restore the pressure in the cylinder. Just as water evaporating from a person's skin cools the person off, the evaporation of the liquid CO2 in the storage cylinder cools off the cylinder (liquid and gas). Over extended use, the cylinder and/or other components of the device will freeze (which ceases operation of the device), unless some counter-acting heating source is employed. As another description of this cooling process, the molecules of the liquid CO2 are generally in constant motion, some moving faster than average, some moving slower. The average speed of the molecules is related to temperature, and the higher the temperature, the faster they generally move. However, when molecules evaporate from a liquid the faster “hot” molecules convert into the gas phase. As these molecules convert to gas, they lose some of their speed breaking away from the liquid, but the liquid that is left behind is colder than it previously was because it lost its “hot” molecules to the gas.
Thus, conventional compressed gas cylinders (which refers broadly to any storage vessel or container) typically have liquefied gas under its own vapor pressure at ambient temperature. As the vapor is withdrawn from the cylinder, the liquid evaporates at an equivalent rate to account for the decrease in pressure. This consumes energy from the remaining liquid in the tank. In the absence of some thermal counter-activity (e.g., heating of the cylinder), the liquid temperature drops, which may lead to a corresponding drop in the vapor pressure. If no thermal counter-activity is taken and the gas cylinder is outputting its gas (e.g., for driving a device) substantially continuously for an extended period of time, the reduced temperature will result in freezing of the cylinder or other components of the device, which causes proper operation of the device being driven by the gas to deteriorate or cease.
Various approaches have been taken with regard to the temperature reduction and potential freezing of CO2-driven devices. One approach, which does not attempt to alter the reduction in temperature, but instead attempts to insulate the cold temperature (e.g., protect a user's hands from the cold CO2 cylinder, etc.) is to cover the cylinder in a thermal insulation material. Merely using insulation does not keep the cylinder at sufficiently high temperatures (e.g., to avoid freezing over extended use) and may actually prevent ambient heat from heating the cylinder, which may encourage faster freezing of the CO2 cylinder in some instances. It should be understood that thermal insulators act to prevent the exchange of thermal energy, and thus isolate the thermal energy that is present on either side of the insulator (e.g., to contain the reduced temperatures generated within the insulator encasing the CO2 cylinder, and to isolate warmer temperatures that may reside on the opposite side of the insulator from being transferred to the cylinder). Similar thermal insulators are commonly used, for example, for encasing a cold beverage, where the insulator aids both in maintaining the beverage cold and in preventing the cold from reaching a user's hand while holding the insulated beverage. Thus, thermal insulators do not perform a heat transfer or exchange, but have been employed in some instances to contain the reduced temperatures generated by a CO2 cylinder within an encasing insulator so not to cause frostbite or significant discomfort due to extreme cold when touching the cylinder.
The reduced temperature and potential freezing of CO2-driven devices has traditionally been addressed in varying ways, depending on the intended application of the compressed gas-driven device. First, there are certain devices that are not expected to encounter extended use. For instance, in certain devices, the CO2 is expended in an unregulated-flow, such as in an explosive-type expulsion. As an example, U.S. Pat. No. 5,149,290 titled “Confetti Canon” (hereinafter “the '290 patent”) describes a device that employs an unregulated flow of CO2 for projecting confetti. For instance, the '290 patent describes a confetti canon that has “a cartridge puncturing mechanism which enables complete discharge of CO2 cartridge contents in less than three seconds,” see the abstract of the '290 patent. Such unregulated flow devices may not encounter freezing due to the quick expulsion of the CO2, rather than extended, regulated use thereof. Accordingly, in many such unregulated flow devices, measures are simply not taken for addressing the reduction in temperature and potential freezing that may occur through extended use of CO2 driving the device.
Other devices exist which employ regulated CO2 flow, but which do not address freezing. For instance, certain devices may be intended for such limited-time intermittent use that the freezing is not expected to become an issue. That is, the use of the CO2 may be intended to be sufficiently intermittent that temperature reduction to an extent that interferes with operation of the device (e.g., freezing) is not expected to be encountered (e.g., sufficiently long recovery periods of non-operation are expected to be present in the intermittent use of certain devices).
As another example, other devices may be intended for extended use, but are implemented to simply accept the reduction in temperature and eventual freezing of the device. For instance, a CO2-driven air chuck may be implemented for use in airing tires (as may be used for roadside emergencies or off-road application, for example), wherein the device does not attempt to counteract, in any way, the reduction in temperature and potential freezing encountered through use of the CO2 but instead accepts that after a certain amount of extended use it will freeze (and the air chuck will cease to operate while frozen).
Certain CO2 devices may be implemented with a piston-driven regulator for regulating the output flow of CO2 from the storage cylinder. Examples of such piston-driven regulators that may be implemented include those disclosed in U.S. Pat. No. 5,411,053 titled “Fluid Pressure Regulator” and U.S. Pat. No. 5,522,421 titled “Fluid Pressure Regulator”, the disclosures of which are hereby incorporated herein by reference. Further examples of piston-driven regulators that be implemented include those commercially known as HyperFlo, HyperFlo2, HyperFloMAX, HyperFloDYN COMPACT available from Offroad Tuff (see e.g., http://www.offroadtuff.com/CO2Regulators.htm). Certain piston-driven regulators are marketed as being “no freeze.” However, such no-freeze regulators themselves do not prevent or counteract freezing from occurring in the CO2 storage cylinder, and over extended, substantially continuous use in dispensing CO2, the no-freeze regulators themselves have been found to eventually freeze if further counteracting measures are not employed.
Certain regulated-flow CO2-driven devices permit extended use and attempt to address reduced temperatures and potential freezing through persistently-maintained, active application of heat to the CO2 storage cylinder and/or other device components. One traditional approach for counteracting the reduced temperatures resulting from substantially continuous use of the regulated-flow, extended-use CO2-driven devices is to implement electrically-powered heater(s) for actively heating the cylinder and/or other components of the device. Such electrically-powered heater(s) provide a persistently-maintained heat source that can persist in actively generating heat for heating the cylinder over periods of extended use.
As one example, the Biomist™ Power Sanitizing System commercially available from Biomist, Inc. (see www.biomistinc.com) is a CO2-driven sanitizing device that employs on-board electrically-powered (i.e., AC-powered) heaters. The Biomist™ Power Sanitizing System employs a siphon-type CO2 cylinder, which discharges liquid CO2. The on-board electrically-powered heaters are used to heat the discharged liquid to convert it to gas, and the gas is then used as a propellant for outputting (e.g., via a spray nozzle) a sanitizing solution. Without the electrically-powered heaters, the desired conversion of liquid CO2 to gas for use as a propellant would not be achieved in the Biomist™ Power Sanitizing System, and eventual freezing of the CO2 cylinder and/or regulator (or other device components) would be encountered after a period of extended, substantially-continuous use so as to interfere with operation of the sanitizing device.
As another example, U.S. Pat. No. 6,043,287 (hereafter “the '287 patent”) titled “Disinfectant Composition and a Disinfection Method Using the Same,” the disclosure of which is hereby incorporated herein by reference, discloses “a disinfectant composition which is suited to the disinfection of confined spaces such as the interior of an ambulance or the like”, see abstract of the '287 patent. The '287 patent further proposes “atomizing and spraying this disinfectant composition by means of a high-pressure gas such as pressurized carbon dioxide gas”. Id. As illustrated in FIG. 1 of the '287 patent and discussed therein (e.g., at column 4, lines 18-29), the '287 patent proposes use of a siphon-type CO2 cylinder with an AC-powered heater. Thus, as with the Biomist™ Power Sanitizing System, the '287 patent proposes a system that relies on electrically-powered heaters for achieving the desired conversion of liquid CO2 to gas for use as a propellant, and without such electrically-powered heaters eventual freezing of the CO2 cylinder and/or regulator (or other device components) would be encountered after a period of extended, substantially-continuous use so as to interfere with operation of the sanitizing device.
As another example U.S. Pat. No. 6,025,576 (hereafter “the 576 patent”) titled “Bulk Vessel Heater Skid For Liquefied Compressed Gases” describes generally “heating a container that stores and dispenses compressed gas and, specifically, with a heater arrangement attached to a skid for heating bulk vessels that store and dispense liquefied compressed gas”, see column 1, lines 5-8 of the '576 patent. In the '576 patent a “heater skid comprises a framework for receiving the cylinder and one or more heaters coupled to the framework so that the received cylinder is proximate to the heaters, thus, allowing the heaters to heat the cylinder”, see abstract of the '576 patent.
Another example of a heating technique that has been proposed for use in gas delivery systems is an active heating/cooling jacket which is placed in intimate contact with the gas cylinder and the jacket is maintained at a constant temperature by a circulating fluid, the temperature of which is actively controlled by an external heater/chiller unit. As examples, U.S. Pat. No. 6,076,359 (hereafter “the '359 patent”) titled “System and Method for Controlled Delivery of Liquified Gases” and U.S. Pat. No. 6,581,412 (hereafter “the '412 patent”) titled “Gas Delivery at High Flow Rates,” the disclosures of which are hereby incorporated herein by reference, each mention use of such an active heating/cooling jacket and/or other techniques for actively heating/cooling gas cylinders, particularly for use in controlled delivery of gas in semiconductor processing.
The '359 patent mentions in its background use of heating/cooling jackets (see column 2 line 59-column 4, line 27 thereof). The jacket is described as being placed in intimate contact with the cylinder and the jacket is maintained at a constant temperature by a circulating fluid, the temperature of which is controlled by an external heater/chiller unit. Thus, some persistently-maintained (e.g., electrically-powered) heater/chiller unit is employed for actively, persistently maintaining the temperature of the jacket at a constant temperature. The '359 patent further describes the use of such a jacket as being problematic for several reasons, and thus proposes a solution that avoids the use of the jacket altogether. In particular, the '359 patent proposes a system that increases the heat transfer between the ambient and the gas cylinder placed in a gas cabinet. The increase is achieved by altering air flow rate in the cabinet and adding fins internal to the cabinet. For instance, at column 9, line 37-column 10, line 37 (and see FIGS. 10-11 of the '359 patent), the '359 patent describes that air may be pulled into the cabinet containing the gas cylinder, and the air may be actively heated with an electrically-powered heating element, such as a hot plate-type heater. The circulating air passing through the cabinet is used to heat the gas cylinder. This is described as enhancing the heat transfer from the ambient to the cylinder.
The '412 patent also appears to propose use of a persistently-maintained, active heating means, such as an electrically-powered heater, for heating a jacket or hot fluid that is in direct contact with the gas cylinder, see e.g., column 4, line 48-column 5, line 35 thereof and see the heaters shown in FIG. 7, which are electrically powered as mentioned in column 10, lines 8-12 of the '412 patent.
U.S. Pat. No. 5,986,240 (hereafter “the '240 patent”) titled “Method and Apparatus for Maintaining Contents of a Compressed Gas Cylinder at a Desired Temperature,” mentions in its background (see column 1, lines 35-52 thereof) that a heating blanket may be wrapped around a cylinder to heat the cylinder. However, the '240 patent describes that the use of such a blanket is not desirable (see column 1, lines 35-48 thereof), and thus goes on to propose use of a persistently-maintained heat source, such as electrically-powered heaters, as mentioned at column 3, lines 2-5 and shown as element 15 in its FIG. 3, for warming the air around the gas cylinder within the cabinet.
As yet another example, U.S. Pat. No. 4,627,822 (hereafter “the '822 patent”) titled “Low Temperature Inflator Apparatus” proposes another type of active heater for heating a CO2 cylinder. The '822 patent proposes use of a non-persistently maintainable heat source for heating a CO2 cylinder. In particular, the '822 patent proposes an inflator assembly (see assembly 10 of FIG. 1 of the '822 patent) for inflating an inflatable life raft or life preserver, where the inflator assembly includes a CO2 cylinder (see CO2 cylinder 15 in FIG. 1 of the '822 patent) for driving inflation of the life raft or preserver. The inflator assembly further includes an on-board solid pyrotechnic gas generator (see generator 16 in FIG. 1 of the '822 patent) that is positioned side-by-side the CO2 cylinder. The '822 patent employs a heat conductive material (see material 19 in FIG. 1 and core 46 and winding 47 of FIG. 3 of the '822 patent), such as aluminum, which conducts heat from the solid pyrotechnic gas generator to the CO2 cylinder, see column 2, lines 25-30 and column 3, lines 8-15. In operation, an actuator punctures the cartridge and ignites the generator, and combustion gas from the generator will begin immediate inflation of the inflatable gear, while heat developed by the generator is transferred to the liquid CO2 for accelerating the venting of high pressure CO2 gas to the gear, see column 1, lines 60-66.
As still another example, U.S. Patent Application Publication No 2004/0050877 (hereafter “the '877 application”) titled “Sterilizing and Disinfecting Apparatus,” the disclosure of which is hereby incorporated herein by reference, proposes “an apparatus for sterilizing and disinfecting a target space by spraying a chemical including alcohol”, see abstract of the '877 application. The proposed apparatus is driven by a compressed gas, such as CO2, that acts as a propellant for dispensing the sterilizing and disinfecting solution. The '887 application describes in its background (see paragraphs 0003-0011 thereof) that traditional such compressed gas-driven sterilizing and disinfecting devices have included electrically-powered heaters. The '887 application proposes a sterilizing and disinfecting apparatus that can “operate with a simple structure requiring no power supply”, see abstract of the '877 application. However, the '887 application recognizes in paragraph 0043 that in “the process of injecting the carrier gas . . . , there is a possibility that volume expansion due to decompression in the pressure reducing valve 2 causes the peripheral part to freeze,” but the '877 application explains that “it is possible to delay the time to freeze by appropriately determining the feed rate of the carrier gas.” Thus, the '877 application does not propose any technique for counteracting the reduced temperature generated by the operation of the compressed gas (e.g., CO2) in driving its apparatus (e.g., acting as a propellant), but instead accepts that freezing may eventually occur, and merely proposes to attempt to delay the occurrence of the freezing through controlling feed rate of the carrier gas.
One particular example of a compressed gas-driven device is a solution dispensing device (e.g., a sprayer, mister, etc.) which employs compressed liquefied gas (e.g., CO2) as a propellant for dispensing (e.g., spraying, misting, etc.) a target solution, such as a sanitizing solution (e.g., a disinfecting and/or sterilizing solution, such as the above-mentioned alcohol-based solutions of the '287 patent and the '877 application), a beverage, a pesticide solution, etc. In many applications of such a device, extended use may be desired which, if not counteracted, may lead to undesirable freezing of the CO2 cylinder and/or components of the device. As in the above-referenced '287 patent, electrically-powered heaters have commonly been proposed for use in persistently generating heat for actively heating the CO2 cylinder and/or components of the device (e.g., to maintain a constant temperature thereof). In some instances, such as in the above-referenced '359 and '412 patents, the heater may actively heat a jacket that is in intimate contact with the cylinder, for example.
However, the implementation of electrically-powered heaters leads to increased weight, size, and cost of the device, and the use of electrically-powered heaters presents potential hazards that render the implementation unsuitable or undesirable for use in many environments in which electrical sparks may present a fire hazard. For instance, pet food production plants, grain silos, or other industrial environments may prohibit use of any electrical outlet or any electrically-powered devices due to the risk of sparking the airborne dust present in the facility. Similarly, other potential ignition sources, such as the pyrotechnic gas generator of the '822 patent, may be unsuitable for many environments because of the potential fire hazard.
Further, the AC powered solution, such as in the '287 patent, limits mobility of the device during operation (e.g., due to being tethered via an electrical cord to an electrical outlet), and it restricts use of the device to locations that have readily-accessible electrical outlets. On-board batteries may be implemented to alleviate the tethering effect of the AC power cord, but this further increases the size and weight of the device (due to the batteries), and still presents a potential electrical spark hazard.